An electric vehicle is equipped with a driving battery that stores power by electric charge. The electric vehicle runs as a motor is supplied with and driven by the power stored in the driving battery. A lithium-ion battery or a nickel-hydride battery, for example, each of which has high energy density, is used as the driving battery. The driving battery is charged from a household outlet or with a quick charger installed at a shopping mall.
The electric vehicle can also supply power stored in the driving battery to equipment at buildings. In particular, a technology is proposed to supply power from an electric vehicle to equipment as a backup power source in power outage (refer to Patent Literature 1, for example).
According to a household power outage backup system of Patent Literature 1, in response to detection of a household power outage, an automotive controller installed in a house transmits a starting signal to an engine starter installed in a vehicle to start an engine. The starting engine drives a power generator mounted in the vehicle. Power generated by the power generator is supplied through a power supply connecter and is converted to an alternating current by a DC/AC inverter installed in the house. The power is then supplied to devices that require an emergency power source.
[Patent Literature 1] Japanese Unexamined Patent Application Publication No. H2-142329
Patent Literature 1, however, does not disclose or teach how the automotive controller and the DC/AC inverter installed in the house are operated without power supply due to a power outage. It is assumed that a dry-cell battery or an emergency battery is probably provided in the house such that power is supplied to the automotive controller and the DC/AC inverter even in a power outage.
Specifically, it is first necessary to control equipment at a building, to receive power supply from the electric vehicle in a power outage in the technology of Patent Literature 1. Furthermore, a power source for the control, i.e., a power storage device, such as an emergency battery, must be installed in the equipment. Since the power storage device is unnecessary other than emergency, such as a power outage, a space for storing the power storage device is a waste in normal time. Furthermore, since a battery spontaneously discharges even if not used, the battery should be replaced periodically with a new one even if unused, thus increasing the maintenance cost.